Many of the individual race forecasts in the FiveThirtyEight Senate model, which launched on Wednesday, look pretty optimistic for Democrats. …
But despite that, the model has Democrats as reasonably clear underdogs to take control of the Senate. Even though it’s more optimistic than the consensus about Democrats’ chances in several individual races — and even though the model is generated by the same program that gives Democrats around a 5 in 6 chance of winning the House — it nevertheless says Republicans have somewhere between a 2 in 3 and 7 in 10 chance to hold the Senate, depending on which version of our model you look at. CONT.
Nate Silver, FiveThirtyEight